The emphasis will remain on viscerosomatic reflex studies. The influence of carotid baro- and chemoreceptors and of pulmonary baroreceptors on alpha motor activity, occurring spontaneously or evoked, will be investigated. The receptors will be excited by nicotinic agents, veratrum alkaloids, phenyldiguanide and 5- hydroxytryptamine, on one hand, and by physiological stimuli, such as local pressure changes and hypoxia, on the other. Electrical stimulation of the carotid sinus nerve and of the recurrent cardiac nerve (from the pulmonary baroreceptors) will also be used. Further, the influence of drug injection into the local blood supply and of distension of the stomach on alpha motor activity will be explored. In order to trace the central and descending pathway of the viscerosomatic reflex the bulbar reticular formation, reticulospinal tracts, and spinal interneurons will be searched for evoked activity following injection of the sensory stimulant drugs. Higher centers may be included to detect the extent of evoked activity following excitation of enteroreceptors. Cholinesterase inhibitors will be added to the drugs currently studied.